WASHINGTON
— CONGRESS is on the verge of opening one door to final ratification of the strategic arms reduction treaty, START II, even as it threatens to close another.

The Senate is expected to approve ratification of the 1993 agreement by a wide margin soon after Congress returns from its holiday recess. But the Russian parliament may not follow suit if American lawmakers continue to press for deployment of an antimissile defense system, which is hotly opposed by Moscow.

President Clinton is expected to veto a defense authorization bill that calls for deploying missile defenses on United States soil by 2003. Yet the issue enjoys wide backing in Congress. It also enjoys the support of virtually all Mr. Clinton's Republican challengers for the White House.

"If [Republicans] make this a major election issue, that will prevent Russian ratification during 1996," says Spurgeon Keeny, president of the private Arms Control Association, in Washington. "If they win the election, it will be the end of START II and of arms reduction for the foreseeable future."

Failure to secure Russian ratification of START II could also jeopardize an agreement, to which the five declared nuclear powers have committed, to halt all nuclear testing next year.

The START II treaty was held up for three months in the Senate Foreign Relations committee because of a dispute between the panel's chairman, Sen. Jesse Helms (R) of North Carolina, and committee Democrats over a Helms plan to reorganize and downsize the country's foreign-policy bureaucracy. It was voted out of the committee two weeks ago after a compromise was reached.

The delay means the ratification vote will be taken up in the new, presumably less hospitable Russian parliament elected last Sunday.

"The chances of ratification are probably less now but there's still a strong case to be made for the treaty and a strong potential base of support," says John Holum, director of the US Arms Control and Disarmament Agency (ACDA).

Smaller arsenals

The START II treaty, together with the already ratified START I treaty, would reduce US and Russian nuclear arsenals to no more than 3,500 warheads each, one-third of their 1990 total.

Experts say the indefinite postponement of START II could interrupt recent progress in arms control capped by this year's indefinite extension of a 1968 treaty to contain the spread of nuclear weapons.

START II has won the conditional endorsement of Russian President Boris Yeltsin. It has also enjoyed the backing of the Russian military since it brings US and Russian nuclear arsenals into balance and thus obviates the need for an economically crippling arms race with the US.

Renegade nukes

US lawmakers say a missile defense system is needed to cope with the threat posed by renegade nuclear states. The Clinton administration itself has advocated the idea of erecting theater missile defenses to protect US troops stationed overseas, which Russia says would be a violation of the 1972 Anti-Ballistic Missile (ABM) treaty.

More worrisome to Moscow is Congress's demand for a US-based multisite missile defense system.

Early deployment would effectively end the ABM treaty, which would be a deal-breaker on START II for the Russians.

Russian officials warn that deployment of ballistic-missile defenses would threaten Russia's remaining deterrent force, ending any incentive to go along with START II. Without START II, Russia could keep its heavy land-based intercontinental missiles that could overwhelm missile defenses.

Any move toward ballistic-missile defenses "could be enormously damaging in the START context," interrupting implementation of START I and sealing the fate of START II in the Russian parliament, Mr. Holum says.

"Faced with a more nationalistic parliament and US endorsement of a national ABM system, the Russian military cannot be expected to carry the torch for START II in the post-Yeltsin era," Mr. Keeny adds.

Keeny says the new Russian parliament will be "more nationalistic, more undisciplined, less informed on START II issues, and more likely to subordinate START to domestic issues in the run-up to the Russian presidential election in June."

If START II is ratified by both nations, it would mark a particularly important milestone for a group of retired senior military officers and defense experts who recently urged that the US and other nuclear nations begin work toward the "progressive elimination of all nuclear weapons from all nations."

Down to zero

Their report, entitled "An Evolving US Nuclear Posture" and issued by the Washington-based Henry L. Stimson Center, notes that the end of the cold war and the declining military utility of nuclear weapons offer an unprecedented opportunity to begin a phased build-down to zero nuclear weapons.

The first phase recommended in the report would begin with the reductions of US and Russian arsenals called for in START II. During stage II, the five nuclear powers (including China, France, and Britain) would agree on equal or proportionate reductions to the "hundreds" range.

During stage III, the declared and undeclared nuclear powers (including Israel, Pakistan, and India) would reduce their arsenals to "tens" of weapons, followed by eventual complete elimination within a framework of international safeguards and verification procedures.

In a press conference last week, retired Gen. Andrew Goodpaster, a former supreme Allied commander in Europe, acknowledged that a nuclear-free world could make conventional war less risky and thus more likely.

But he said the risks of conventional war are dwarfed by the risks of nuclear conflict.

"In this world you have to think in terms of greater objectives and lesser objectives," General Goodpaster said. "The prudent course is to go for the greater objective."